In an automobile as a mobile body, generally, various electric devices are mounted like lamps such as a head lamp and a tale lamp, motors such as a starter motor and an air conditioner motor.
In order to supply power to the aforementioned various electric devices, junction blocks are located optionally in the automobile in position. The junction blocks are integrally composed of various electric circuit units such as a number of fuses or relays.
Note that the junction block is also called fuse block, relay block, or electric junction box collectively because it may include fuses, relays and bas bars. The aforementioned fuse block, relay block, and junction block is hereinafter called electric junction box.
An electric junction box conventionally employed includes a box main body, and a wiring unit accommodated in the main body. The main body is flatly box-shaped. The main body includes a lower cover and an upper cover attached to each other and accommodating a wiring unit. The lower cover and the upper cover are made of isolating synthetic resin and are formed by injection molding.
The wiring unit is provided with a printed wiring board, a plurality of connectors mounted on the printed wiring board, a fuse holder holding a plurality of fuses mounted on the printed wiring board, a plurality of relays mounted on the printed wiring board. Conductive trace of the printed wiring board electrically connects each of terminals of the connector, the fuses, and the relays according to predetermined traces.
The connector is exposed to outside the main body through a through hole passing an outer wall of the main body. At least one of the connectors is engaged with a connector attached to a power cable terminal connected to power source such as a battery or a power generator installed in the automobile. The other connectors are engaged with connectors attached to wire harness terminals connected with various electric devices mounted in the automobile.
The fuse holder is exposed to outside the main body through the through hole passing the outer wall of the main body. The fuse holder has a plurality of fuses. The relay is mounted on the printed wiring board, and accommodated in the main body.
The aforementioned conventional electric junction box makes power supplied from the connector connected from the power source branch into conductive traces of the printed wiring board, pass the aforementioned fuses and the relays, and supply with various electric devices via the wire harness.